1989 325i making unearthly noise under the engine

Let me try to describe the sound. It doesn't happen all the time, just after a lot of driving. Occurs when turning, especially on uneven road surfaces. It can happen when I brake, though I don't
think it's the brake pad sound. It can continue even after I have fully braked, and the car is standing still. It can happen when I decelerate, am close to braking. It seems to come from the middle front, i.e., almost under the airconditioning system. Perhaps a little on the left, though it's hard to tell. It's not quite grinding, not quite clanging, not quite rattling, not quite groaning/moaning, though a little of all of these. Definitely metallic. The best I can describe is it sounds like a plane going overhead, and I often have to look if there's a plane, or a truck or something beside or behind me making the sound. Recently the car was parked for almost 2 mos., during Houston 100 degree heat, at a stupid mechanic's. The noise started after that. I'd really appreciate help as to what this might be. Before I take in to another mechanic, not the same one. Thank you!
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Kind of hard to tell with that explanation but I'd look real hard at the motor mounts. If your engine is moving around it can make all kinds of bad sounds. If you still have the original mounts they are ripe for a failure.
RJD
On Mon, 24 Aug 2009 23:21:04 -0700 (PDT), AnisShivani

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Could it some suspension part that's dried up because the car stood for so long? And just needs to be lubricated? I'd guess it's something frozen, or has come loose, because they didn't reassemble things properly. By the way, they were working on the a/c for all that time. How about a loose wheel bearing? Is that possible?
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I had similar sounds and it ended up being a bad alternator along with bad pulleys/bearings. How many miles on car? I've learned bmw autos have weak cooling systems (factory). Also alternators and the pulleys/bearing don't last as long as japanese cars. I've seen them go about every 35k or so. Japanese alternators, pulleys and bearing usually go over 100k miles. since u car is 89 model, I'd also look at motor mounts, suspension bushings too.
However the sound u describe sounds like something spinning at high speed that has broken.
Good luck!!
Oskar
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Thanks for your thoughts. The car has around 180,000 miles on it. I've had it for ten years and never replaced the alternator, or pulleys/bearings. It's generally trouble-free, unless the mechanic messes it up, makes it worse than when I left it there. I still think something dried when it was parked for 2 mos., and perhaps has broken now. Is suspension bushing/ mounts/bearings work expensive to fix?
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In article

New one on me. The alternator maker supplies others too.

Don't think I've ever had an alternator bearing fail. Electronic failure usually gets them first. The one on my E34 525 failed at approx 150,000 miles - and I could probably have fixed it but had to have it replaced since it failed some way from home. The most likely failure is the regulator followed by the diode pack. Never seen worn out brushes either.
Later engines have problems with the idler pulleys.
--
*Never put off until tomorrow what you can avoid altogether *

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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